Rocket propulsion method



July 28; .1959

- A. ZLETZ ETAL ROCKET PROPULSION METHOD Filed Feb. 16. 1953 I OX/DIZER F INVENTORS A/ex Z/efz .000 R. Caimody mz@ I firm- U te tr w Pw O 11]., assignors to Standard Oil Company, Chicago, 111.,

a corporation of Indiana Application February 16, 1953, Serial No. 336,903

13 Claims. 01. 6035.4)

This invention relates to the generation of gas. More particularly, it relates to reaction propulsion by the hypergolictreaction of a liquid fuel and a liquidoxidizr. Still more. particularly, the invention relates to a method of rocket propulsion by the hypergolic reaction of a fuel and a hydrogen peroxide oxidizer, which materials spontaneously react to generate gas at high pressure and high temperature. f V f Reaction propulsion is now. being used for many aerial purposes. For many'uses it is necessary to operate with a fuel system which is not dependent on atmospheric oxygen..xThis fuel system may consist of a'single self-contained propellant or it mayconsist of a separate fuel and a separate oxidizer, i.e., a 'bip'ropellant system.

In" the bipropellant system the fuel and the oxidizer are introduced separately and essentially.simultaneously into the combustion chamber of the reaction motor. The products of oxidation from the reaction of the fuel and the oxidizer are discharged through an orifice at the exit end of the combustion chamber and thereby. produce the driving force. Because of the possibilities of elec trical and/or mechanical failure ofthe auxiliary methods of ignition such as a spark or'a' hot surface, it is preferred to use a self-igniting fuel system. A fuel which is self-ig-f 2 ammonium nitrate. Thus a solution containing 40 weight percent of ammonium nitrate and in which the hydrogen peroxide-water portion contains 90 weight percent of H 0 has afreezing point of about --30 F. A so-called 80% H O 3O% NH NO solution has a freezing point of below 70 F.

Concentrated aqueous hydrogen peroxide solutions have been used as monopropellants by catalytically 'de composing the hydrogen peroxide usinglsuch catalysts as potassium permanganate or copper oxide. Since, the decomposition products contain free-oxygen the monopropellant system is ineflicient. However, fuels which are hypergolic with nitric acid oxidizers may bemuch less active or even inactive with concentrated H 0 solutions. Anhydrous hydrazine is usually considered to be.

the only fuel that is sufficiently hypergolic with concentrated H 0 solutions to be practical; however, hydrazine niting, i.e., spontaneously combustible when contacted.

withan oxidizer, is known as a'hypergo'lic fuel. I. Temperature has an importantelfection'thehypergolic. activity of fuels. .The temperatureiat the earths surface may vary from a high of about +125 C Filto alow ofIas much as '65 F.; in. general temperatures below about 20f. or 30 F. -are exceptional. Thus surface-to-air missiles or.rocket-driven aircraft should'be capable'of operation when the temperature of thefuel and the oxi-v dizerat the moment of initial contact'in the combustion chamberof the rocket motor is on the order of --20 F. Temperatures at high altitudes are frequently on .the order of 65 F. and are knowntoapproach -100.1F.. :.Thus an air-.to-air missile should be able to operate satisfactorily when'the temperature of :the fuel and the oxidizer. at the moment of initial contacting 'in' the :combustion chamber is on the orderof 65 F.

. Thelmore' commonfoxidizers. alrel'white fuming nitric acid, red fuming'nitr'ic acid and l=nitticf acid sulfiiric acid mixtures; While these nitriclacicl oxidizers operate sat: isfactorily over a wide range .ofatmosphefictemperatures'nthey .have important zdrawbacksz The nitric: ac'id oxidizers are extremely corrosive; they havepoor=storage stability; they give off toxic gases; and special precautions must be taken by personnel who handle these oxidizers. Concentrated" "aqueous hydrogen peroxide solutions have excellent storage stability and do not give off harmin; gas. Hgw er, thesaqneons hydrogen peroxide sblu-f tions s as 90% YdF EQ fWIQX lQ1 W??? q s va i. tage I of comparatively high. freezing points, e.g 90%- hydrogen peroxide solution freezes at +12- F. v. The freezing pointz.of.80% hydrogen peroxide .9. F.',,bu t ,the activity of thissolution", toward the prior 'ar'tjfuels l is markedly lower than the 90% H 0 solution. The freez-; ing pbintofaqueous hydrogen peroxide Sblutionscan'be deman sq v t erein g d s n a t p lzly.

has the disability of a comparatively high freezing point. Some fuels are operative with H 0 solutions in the presence of an H 0 decompositon catalyst. Furthermore, the prior art fuels are less effective with ammonium nitrate containing aqueous hydrogen peroxidethan with aqueous hydrogen peroxide alone.

An object of this invention is a method of generatifig. as by the hypergolic reaction of a fuel and a hydr peroxide oxidizer. Another object is a method of reaction propulsion by the hypergolic interaction of a fuel and a hydrogen peroxide oxidizer. Still anotherobject is a method-of reaction propulsion by the hypergolic interaction of a hydrogen peroxide oxidizer and a fuel which.

contains appreciable. amounts of hydrocarbons, particularly non-hypergolic liquid hydrocarbons. A particular object is a method of generating gas by. the hypergolic interaction of a defined fuel and an oxidizer consisting of an aqueous hydrogen peroxide solution containing dis-. solved ammonium nitrate. is a method of rocket propulsion by the hypergolic interaction of a defined organic haloamidophosphite and a defined hydrogen peroxide oxidizer. when the temperature of the fuel and the oxidizer. is above about 70 F. Other objects will become apparent in the course of the detailed description of the invention.

A method has been discovered for generating gas, which gas may be used as a substitute for compressedair for certain purposes or for driving the turbine of .a jet engine or for rocket propulsion, which method comprises contacting (1) A hypergolic fuel consisting essentially of a halo .amidophosphite selected from the class consisting of i (i) dialiphaticdihaloamidophosphites containing from 2 to 12 carbon atoms and ii di-dialiphatichalodiamidophosphites containing from 4 to 16 carbon atoms and not more than 6 carbon atoms in one aliphatic radical and wherein the halogen radical is selected from the class consisting of chlorine and bromine, and An-oxidizer selected from the class consisting of v (a) -Aqueous hydrogen peroxide solutions which and the remainder is essentially water and A mixed fuel madeup 'of dialkylhaloamidophosphite wherein each. alkyl radical contains from 1 to 3 carbon atoms which contains as much as 30 volume percent of miscible hydrocarbonris hypergolic with aqueous hydrogen peroxide-ammonium nitrate solutionscontaining at; least about 90 weight percent of hydrogen peroxide the. Hzoew P n l. ante sxi r ar al:

P aiented July 28, 1959 Another. particular. object contain at least about Weight percent of H 0 3 a temperature of about -20 F. The higher the temperature of initial contact the more hydrocarbon that is tolerable in the mixed fuel.

Certain organic haloamidophosphites ignite spontaneously when contacted with hydrogen peroxide oxidizers. The various haloamidophosphites do not have equal hypergolic activity with the same oxidizer. However, by proper selection of the haloamidophosphite, it is possible to obtain a hypergolic reaction with a tolerable ignition delay when the haloamidophosphite and the oxidizer are at a temperature of about -70" F. at the moment of initial contact in the gas generating chamber.

These organic haloamidophosphites have the generic empirical formula (R N),,PX where 1 represents the element phosphorus, N represents the element nitrogen, X represents a halogen radical selected from. the class consisting of chlorine and bromine, and R represents an aliphatic hydrocarbon radical, and wherein e is 1 or 2, g is 1 or 2 and the sum of e and g is 3. Thus these fuels may be dialiphaticdihaloamidophosphites, (R N)PX or di-dialiphatichalodiamidophosphites, z hP s The haloamidophosphites which are suitable for the purposes of this invention contain aliphatic hydrocarbon radicals which may be parafiinic, e.g., methyl, ethyl, isopropyl and butyl; or olefinic, e .g., ethenyl, propenyl, pentenyl, or acetylenic e.g. ethinyl and propinyl; or cycloalkyl or cycloalkenyl, e.g., cyclopropyl and cyclobutenyl.

In the case of the dialiphaticdihaloamidophosphites, the total number of carbon atoms should be between 2 and 12; while in the case of the di-dialiphatichalodiarnidophosphites, the total number of carbon atoms should be between 4 and 16 and not more than 6 carbon atoms should be present in any one aliphatic radical.

The most suitable haloamidophosphites for the purposes of this invention are the dialkylhaloamidophosphites wherein the alkyl radicals contain between 1 and 3 carbon atoms; for example, dimethyldichloroarnidophosphite and di-diethylbromodiamidophosphite. For operationwhere the fuel and the oxidizer will be at a temperature of about 70 F. at the moment of initial contacting of the fuel and the oxidizer, the preferred fuels are the dihaloamidophosphites. n

A mixed 'fuel which is suitable for the generation of gas can be made by mixing haloamidophosphites with miscible hydrocarbons. The minimum amount of haloamidophosphite necessarily present in said hypergolic mixed fuel will vary with the type of hydrocarbon, the

desired temperature of operation and thetypeof H oxidizer. For example: As much as 30% of a petroleum fraction is tolerable in a hydrocarbon-diethylchloroamidophosphite blend which must be hypergolic at about -25 F. when using an ammoniumnitrate containing 90% hydrogen peroxide oxidizer. In general petroleum hydrocarbon fractions are suitable materialsas for example those fractions boiling between about 300 and 600 F. which correspond to the fuel requirement of military jet engines. Aromatic hydrocarbons which boil below about 600 F. are suitable hydrocarbons for this purpose. The hypergolic activity of, the mixed fuel can be improved at lower atmospheric temperatures by using as the hydrocarbon component olefinic hydrocarbons such as thermally cracked napthas and gas oils or turpentine. Conversely, at higher atmospheric temperatures a hypergolic mixed fuel containing less haloamidophosphite is obtainable bythe use of unsaturated hydrocarbons.

The oxidizers of this invention are either concentrated aqueous hydrogen peroxide solutions or aqueous hydrogen peroxide solutions containing dissolved inorganic. salts for example, ammonium halides, sodium sulfate, sodium nitrate, etc.; for low temperature operation requiring a short lgnition delay, ammoniumnitrate must be used as the salt. The concentrated aqueous hydrogen peroxide solutions should contain at least about 80 weight percent of H 0 the remainder of the solution is essentially water.

The hypergolic activity of the aqueous hydrogen peroxide solution is improved by increasing the concentration of the peroxide. Commercially available 90% H 0 solution is an excellent oxidizer for operation above 0 F. For low temperature operation it is preferred to use aqueous H O -amn onium nitrate solutions, such as 90%-40%. or 80%-.30% solutions.

Concentrated aqueous hydrogen peroxide solution as made commercially is virtually only H 0 and water. In order to improve storage stability small amounts of stabilizers are commonly added to the solution, e.g., sodium stannate, tetrasodium pyrophosphate, adipic acid, tartaric acid; in general only trace amounts of stabilizers are added so that thesolution consists essentially of hydrogen peroxide andwater. h

In order to depress the freezing point of aqueous hydrogen peroxide solutions soluble inorganic salts are dissolved therein, e.g., sodium nitrate, potassium nitrate and ammonium nitrate have been used. These salt-containing solutions are commonly designated in terms of the weight percent of salt in the total solution and the weight percent of hydrogen peroxide present in the aqueous portion of the solution, e.g., 90% H O NH NO indicates that the total aqueous hydrogen peroxidenitrate solution consists of 40 weight percent of ammonium nitrate and 60 weight percent of aqueous hydrogen peroxide composed of of 90 weight percent of H 0 and the remainder essentially water. This particular solution has a freezing point of -30 F. A temperature of 7.0 F. is attainable with an 80% H O 30% NH NO solution. -It is preferred to operate in the and tri-dibutyltriamidophosphite.

presence of ammonium nitrate because of the pronounced favorable effect on the hypergolic activity of the fuels of this invention.

It has also been found that tri-dialiphatictriamidophosphites having the empirical formula (R N) P where R represents an aliphatic hydrocarbon radical containing from. 1 to 4 carbon'atoms is hypergolic with the above defined H 0 oxidizers. Examples of these fuels are tridimethyltriamidophosphite, tri diethyltriamidophosphite The hypergolic activity of these fuels atlower temperatures can be greatly improved by adding thereto small, amounts of the above defined haloamidophosphites, i.e., the haloamidophosphites have a synergistic catalytic efiect on the activity of the amidophosphites. For low temperatures the halo arnidophosphite-amidophosphite fuel should contain between about 1 and 50 volume percent of the haloamidophosphiter According to the procedure of Michaelis and Luxembourg, Ber. 28, 2205 (1895), phosphorus trichloride was reacted with diethylamine (1:6 mol ratio) in an ether solution in a 3-necked flask provided with a stirrer and a Dry-Ice condenser. The reaction mixture was maintained at about 0 C. for some hours. The solid product was filtered otf and the ether stripped from the liquid product. The liquid product was fractionated under a pressure ofabout 1 mm. of Hg.

'Three fractions were of interest and the characteristics of these are shown below: r

' Fraction No.

Fraction?, usist s a m ur o m d l ethylan idophosphite and dichlorodiethylamidophosphite.

, Fraetion 3 consisted of a mixtureiof monochlorodi-dia ethylamidopho sphite 37 wt. percent) a tri-diethy1triamidophosphite (63 wtlpercent). t Fraction 4 consisted of tri-diethylamidophosphite and some monochlorodi-diethylamidophosphite. I v u The ignition characteristics of various fuels were studied using a fdrop test. This method utilizes a test tube, 1 in. x 4 in., containing about 0.5 ml. of oxidizer. The fuel to be tested was drawn into a hypodermic syringe. Itwas then ejected forcibly against the oxidizer surface by depressing the syringe plunger. -By this method amounts of fuel of as little as 0.01 ml. can be added. Low temperature tests were carried out by cooling the test tube and the oxidizer contained therein by means of a bath; a drying tube inserted into the top of the test tube excluded moisture. The fuel was cooled separately to the desired test temperature. By supercooling it was possible to carry out tests at temperatures below the freezing point of the fuel and/or the oxidizer.

The ignition delay, which is the time elapsing between the addition of fuel to the oxidizer and visualignition thereof, was determined as either (a) very short which corresponds to substantially instantaneous ignition, (5) short, which corresponds to substantially less than 1 second, and (c) more than 1 second, which time .was

determined by a stop watch.

The following tests illustrate the activity of the haioamidophosphites of this invention and hydrazine wlth hydrogen peroxide oxidizers. r 1

Test 1 In order to observe the elfectiveness of the various fractions described above with oxidizers consisting of aqueous hydrogen peroxide-ammonium nitratesolutions, several runs were made at various temperatures using 0.5 ml. of various hydrogen peroxide oxidizers.

For comparative, purposes hydrazine vvas contacted at various temperatures with various H 0 solutions as the oxidizer.

Run H2O; Fuel Temp. No. oxidizer, added, F. Ignition delay percent ml.

90 0. 05 +70 Very short. 11 80 0. 03 +70 Short. 12 80 0. 10 +14 N o ignition (effervescence). 13 90-40 0. 03 +14 No ignition. 13a-. 90 0. 03 +14 Very short.

Test Ill The hypergolic activity of mixtures of Fraction 3 and n-octane was tested using various hydrogen peroxide oxidizers.

Mixed fuel n- F 1 0e ane ue Run conadded, Oxidizer 'lemp., Ignition No. tenlt, ml. HzOr-NH4N05 F. delay percent 14... 0.06 90 +70 No ignition (effervesoence). 15.- I 25 0. 12 90 +70 Short. 16--- 34 0.16 90 +70 No ignition. 17 25 0. 04 90-40 +70 Very short. 18"--. 25 0.06 90-40 22 No ignition (offer- 7 vescenee). 19.---. 25 0. 10 90-40 -25 Short.

Runs 15 and 17 show the very favorable effect on ignition delay of the presence of ammonium nitrate in the hydrogen peroxide. 1 H v, j

It is obvious from the data presented above that this invention can be used to generate gas at high pressure. This gas can be used for operating machinerysuch as compressed air hammers or for aircraft catapults; another important use for this high pressure gas is in the starting of the turbines of jet-type engines The invention is particularly useful in aerial missiles which require a compact power plant that develops large amounts of energy over a very short period of time. 1. Other examples of the use of this invention area-the rocketassisting takeofi or flight of aircraft; aerial missiles boosters for surface vehicles. v

The relative proportion; of oxidizer-to-fuel used will depend upon the type of operation, the temperat'urevof operation and the type of fuel and oxidizerbeing used. When using a %40% hydrogen peroxide-ammonium nitrate solution as the oxidizer and di-dimethylchlorodiamido-phosphate as the fuel, between about .4 and 5 volumes of oxizider are needed per volume of fuel.

By way of example this invention is applied to the propulsion of a surface-to-air missile. The annexed figure which forms a part of this specification shows schematically the bipropellent feed system and the motor of this missile. This same type of missile could be used as an air-to-air missile. This missile is suitable for operations wherein the fuel and the oxidizer can be maintained at a temprature high enough to insure at least a short ignition delay, e.g., when using ammonium'nitrate containing H 0 solution as the oxidizer and di-dimethyl chlorodiamidophosphite as the fuel, a temperature of about 70 F.

In the drawing vessel 11 contains a quantity of gas at high pressure; this gas must be inert withrespect to the oxidizer and the fuel; suitable gases are nitrogen and helium. Herein helium is used as the inert gas. Helium from vessel 11 is passed throughline 12 and through valve 13 which regulates the flow of gas to'maintain'a constant pressure beyond valve 13. From valve 13 helium is passed through lines 14 and 16 into vessel "17 and simultaneously through line .18 into vessel 19.

Vessel 17 contains the oxidizer.

valve 22. Valve 22 is a solenoid actuated throttling valve. Suitable electrical lines connect valve 22 to an electrical source and operating switch" (not shown) at the control chamber at the launching site. The oxidizer is passed through line 23 and injector 24 into combustion chamber 26. Combustion chamber 26 is provided with an outlet nozzle 27. 1

Vessel 19 contains the fuel. Vessels 17 and 19 are constructed to withstand the high pressure imposed by the helium gas. The gas pressure forces fuel from vessel 19 through line 28 to solenoid actuated throttling valve 29. Valve 29 is similar in construction and in actuation to vale 22. The fuel is passed through line 31 and injector 32 into combustion chamber 26.

Valve 22 and 29 are of such a size and setting that a predetermined ratio of oxidizer-to-fuel is passed into combustion chamber 26. Injectors 24 and 32 are so arranged that the streams of oxidizer and fuel converge and contact each other forcibly, resulting in a very thorough intermingling of the fuel and the oxidizer.

The missile is launched by activating the solenoids on valves 22 and 29. In this example 4.7 volumes of oxidizer per volume of fuel is introduced into the combustion chamber. The oxidizer and the'fuel react almost instantaneously uponcontact in the combustion chamber; a large volume of very hot gas is produced in the combustion chamber, which gas escapes through orifice 27. The reaction from this expulsion of gas drives the missile toward its target. a

Helium pressure forces the oxidizer out of vessel 17 through line 21' to,

1. A method of generating gas, which method comprises injecting separately and essentially simultaneously hydrogen peroxide solutions consisting of at least about 80 weight percent of H and the remainder essentially water and (b aqueous hydrogen peroxide-ammonium I nitrate solutions wherein the hydrogen peroxide-water portion is the predominant component and consists of at least about 80 weight percent of H 0 and the remainder bustion of the fuel. p

2. The method of claim 1 wherein said fuel is monochlorodi'diethylamidophosphite.

3. The method of claim 1 wherein said fuel is dichlorodi-aethylamidophosphite.

4. The method of claim I wherein said fuel is dichlo-v rodimethylamidophosphite;

5. The method of claim 1 wherein said oxidizer con-,

sists of about 80 weight percent of H 0 and the remainder essentially water.

6. The method of claim 1 wherein said oxidizer consistsof about 90 weight percent of H 0 and the remainder essentially water.

' I '7. The method 0t claim 1 wherein said oxidizer consists of a solution of hydrogen peroxide, water and ammonium nitrate, wherein the nitrate content is about 30 weight percent and the hydrogen peroxidewater portion consists of about 80 weight percent of H 0 and the remainder essentially water.

i 8. The method of claim 1 wherein said oxidizer consists of a solution of hydrogen peroxide, water and ammonium nitrate, wherein the nitrate content is about 40 weight percent and the hydrogen peroxide-water portion consists of about 90 weight percent of H 0 and the remainder essentially water.

1 Thushaving described the invention,'what is claimed essentially water, inan amount and at a rate suificient to initiate a hypergolic reaction with and to support corn- 7 diethylamidophosphite and (2) an oxidizer selected from the class consisting of (a) aqeous hydrogen peroxide solutions consisting of at least about weight percent of H 0 and the remainder essentially water, and (15) aqueous hydrogen peroxide-ammonium nitrate solutions wherein the hydrogen peroxide-waterportion, is the predominant component and consists ofat least about 80 'weight precent of H 0 and the remainder essentially water, in an amount and at a rate sufiicient to initiate a hypergolic reaction with and to support combustion of the mixed fuel n n 10. The method of claim 9 wherein said hydrocarbon is a'liquid petroleum fraction boiling between about 300"; and about 600 F. a

11. The method of claim 9 wherein said hydrocarbon is a liquid aromatic hydrocarbon boiling below about 600 F. a

12 The method of claim 9 wherein saidhydrocarbon is a liquid olefin boiling below about 600 F.

13. A method of generating gas, which method comprises injecting separately andessentialiy simultaneously into the combustion chamber of a gas generator (1) ahypergolic mixed fuel consisting essentially of (l) a liquid miscible hydrocarbon'and (II) dichlorodiethyb amidophosphite and.(2) .an oxidizer selected from the class consisting of (:1) aqueous hydrogen peroxidesolutions' consisting of at least about 80' weight percent of H 9 and the remainder essentially water, and (b) aqueous hydrogen peroxide-ammonium nitrate solutions wherein the hydrogen peroxidewater portionconsists of at least about 80 weight percent of H 0 and the remainder essentially water, in an amount and at a rate suificient to initiate a hypergolic reaction with and, to support combustion of the mixed fuel.

References Cited in the file of this patent UNITED STATES PATENTS Schrader et al. Feb. 7, 1939 Lipkin Feb. 7, 1939 

1. A METHOD OF GENERATING GAS, WHICH METHOD COMPRISES INJECTING SEPARATELY AND ESSENTIALLY SIMULTANEOUSLY INTO THE COMBUSTION CHAMBER OF A GAS GENERATOR (1) A HYPERGOLIC FUEL CONSISTING ESSENTIALLY OF A HALOAMIDOPHOSPHITE SELECTED FROM THE CLASS CONSISTING OF (I) (R2N) PX2 CONTAINING NOT MORE THAN 12 CARBON ATOMS, AND (II) (R2N)2 PX CONTAINING NOT MORE THAN 16 CARBON ATOMS AND NOT MORE THAN 6 CARBON ATOMS IN AN R GROUP, WHEREIN THE R GROUPS IN (I) AND (II) ARE ALIPHATIC, THE X RADICALS ARE SELECTED FROM THE CLASS CONSISTING OF CHLORINE AND BROMINE, N IS NITROGEN AND P IS PHOSPHOROUS AND (2) AN OXIDIZER SELECTED FROM THE CLASS CONSISTING OF (A) AQUEOUS HYDROGEN PEROXIDE SOLUTIONS CONSISTING OF AT LEAST ABOUT 80 WEIGHT PERCENT OF H2O2 AND THE REMAINDER ESSENTIALLY WATER AND (B) AQUEOUS HYDROGEN PEROXIDE-AMMONIUM NITRATE SOLUTION WHEREIN THE HYDROGEN PEROXIDE-WATER PORTION IS THE PREDOMINANT COMPONENT AND CONSISTS OF AT LEAST ABOUT 80 WEIGHT PERCENT OF H2O2 AND THE REMAINDER ESSENTIALLY WATER, IN AN AMOUNT AND AT A RATE SUFFICIENT TO INITIATE A HYPERGOLIC REACTION WITH AND TO SUPPORT COMBUSTION OF THE FUEL. 